Mining Hardware and Software
Various types of hardware can be utilized to engage in Bitcoin mining. The list below is an evolution of the hardware used for mining. The hardware at the earliest stages of mining is now so inefficient that individuals that utilize them actually lose money on the cost of running the equipment over the amount of bitcoins they would discover.
Early Bitcoin client versions allowed users to use their CPUs to mine. This was economically feesible at that time because the rate of discovery was so high. As more users began to mine and with the advent of GPU mining, CPU mining became financially unwise. For all intents and purposes, CPU mining is dead.
GPU Mining is drastically faster and more efficient than CPU mining. It was the next step in the bitcoin mining arms race. Much time, energy, and physical capital was invested into GPU mining rigs but ultimately because the GPU was not specifically designed to mine for bitcoins, newer technology would make mining with this hardware obsolete.
FPGA mining is a very efficient and fast way to mine, comparable to GPU mining and drastically outperforming CPU mining. FPGAs typically consume very small amounts of power with relatively high hash ratings, making them more viable and efficient than GPU mining. Though with the advent of ASIC mining, this may not remain true for long.
In the early part of 2013 specifically designed integrated circuit boards, or application-specific integrated circuit (ASIC), were manufactured for the expressed purpose of mining bitcoins. These tiny chips consume far less power and are exponentially faster at hashing make them the perfect hardware at the moment for mining bitcoins. With the advent of these chips, it will soon be unwise to utilize any other hardware for bitcoin mining.